ABS light on, front ABS works and rear doesn't?

[volkswagensRus]

Alright confusing story. I'd rather give too much info than not enough.

Bought the car a few weeks ago.
When just running during the day, the ABS light is always on. The front ABS seems to pulse the pedal, but the rears will DEFINITELY lock up on me.


At night:
I turn my headlights on, my red BRAKE light illuminates, occasionally flashes while going down the road. Also, ALL 3 rear tail lights light up, but they all get even brighter when I hit the brake.



Whats the deal w/ my ABS? Is it a bad ABS module? Is it something else? Where do I even start?

[rockbeau25]

Check wheel speed sensor. I had the abs module issue but the lights didn't go off until I replaced the wheel speed sensors.


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[volkswagensRus]

The prior owner CLAIMED he went through and checked them all and he thinks they are fine (he was also a mechanic at Volkswagen and has built many cars.). But I do know that I shouldn't necessarily take his word for it.

Would a speed sensor allow the front abs to work but not the rear?

[crazyquik22023]

Check to make sure that all of the taillights and brake lights have the correct bulbs in them and that the "circuit board" the bulbs attach to are not corroded. I have seen your symptoms happen before when there is either corrosion, wrong bulbs installed, and I have also seen it happen when some aftermarket HID bulbs are installed.

[volkswagensRus]

Interesting!! If you look at my thread history, I also have an issue with my BRAKE dash alert, my third brake light is on all the time when the headlights are on, and when the headlights are on the front left turn signal comes on w/ teh brake pedal being pushed.

[LA4]

From my experience, pulsating in the brakes = bad wheel speed sensor. Use VAG-COM to determine which one it is.

I have had 2 separate ABS modules fail on me. In the case of both failures, I had the ABS light flashing and the BRAKE warning light on the dash. There was no pulsing in the brakes though, in both instances with failed modules the car drove fine, just without anti-lock brakes.

[volkswagensRus]

The pulsing (abs modulation?) ONLY occurs during moderate to heavy braking.... if I'm just putting around town, no modulation in the pedal. I'll grab a buddies vagcom and and see if its a wheel sensor though, thank you.

[volkswagensRus]

Any more advice on this? Is my only option at this time to run vagcom and check for wheel speed sensors? Meeting w/ my buddy soon to run some scans and would like to know anything else to check.

[walky_talky20]

For a more detailed interrogation of the sensor outputs, you can use an oscilloscope to view the AC millivolt waveforms produced by each sensor. This is a sort of "fancy pants" procedure. It generally doesn't get that far (or people just start throwing parts at it before ever getting that detailed with a diagnosis).

You say BRAKE light comes on with headlights. Is there any shenanigans with the headlights? Aftermarket HID, etc? "Halo" housings? Ebay LED strip nonsense?

[volkswagensRus]

Headlights and fogs appear stock.

What I've noticed is that when I hit the brake light, the front left blinker comes on like a brake light. It's an amber color. The right front turn signal works as normal, but is an actual white.

When the headlights are on, the third brake light comes on automatically, and the letters "tail light" or something like that comes on.

My ABS light is also on nonstop, but not sure if thats all intertwined.

[volkswagensRus]

Alright so you guys were right; it APPEARS to be only wheel sensors. Rear left one says signal implausible; potential wiring issues? Front right one looks to be fried. This done via vagcom. Will keep you guys updated.